''Bathylychnops exilis'', the Javelin spookfish, is a species of

barreleye Barreleyes, also known as spook fish (a name also applied to several species of chimaera (fish), chimaera), are small deep-sea Argentiniformes, argentiniform fish comprising the family (biology), family Opisthoproctidae found in tropical-to-temp ...

found in the northern

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

and in the eastern

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

near the

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

where it is found at depths of around . This species grows to a length of SL. The species is notable for unusual protuberances that grow from its eyes, which each have "a well developed lens"Pearcy WG, Meyer SL, Munk O (1965). A 'Four-Eyed' Fish from the Deep-Sea: ''Bathylychnops exilis'' Cohen, 1958. ''Nature'' 207, 1260-1262. and a retina, and which have led to the species being called a "four-eyed" fish. They have two spherical eyes that are dorsally directed and two secondary eyes that are ventrally directed. It has been suggested that the purpose of these extra eyes is detection of threats from below, since these eyes point downwards. The Javelin spookfish have a distinct and advantageous secondary globe to their eyes. They use mirrors to collect and focus light, instead of a lens to divert the path of light. This feature provides great benefits in their chances for survival.

References

Opisthoproctidae Taxa named by Daniel Morris Cohen Fish described in 1958 {{Argentiniformes-stub